The present invention relates to perpendicular magnetic recording media, and more particularly relates to multilayer media including exchange decoupled spacer layers.
Perpendicular magnetic recording systems have been developed for use in computer hard disk drives. A typical perpendicular recording head includes a trailing main pole, a leading return pole magnetically coupled to the main pole, and an electrically conductive magnetizing coil surrounding the main pole. The bottom of the return pole has a surface area greatly exceeding the surface area of the tip of the main pole. Conventional perpendicular recording media typically include a hard magnetic recording upperlayer and a soft magnetic underlayer which provides a flux path from the trailing write pole to the leading return pole of the writer.
During recording operations, the perpendicular recording head is separated from the magnetic recording media by a distance known as the flying height. The magnetic recording media is moved past the recording head so that the recording head follows the tracks of the magnetic recording media, with the magnetic recording media first passing under the return pole and then passing under the main pole. Current is passed through the coil to create magnetic flux within the main pole. The magnetic flux passes from the main pole tip, through the hard magnetic recording track, into the soft underlayer, and across to the return pole.
One of the strongest candidates for perpendicular magnetic recording media includes a multilayer structure. Among the advantages of multilayers are easily adjusted anisotropy by varying the thickness of the layers in the bi-layer structure, and a remanence squareness equal to one which ensures media with substantially no DC noise.
Multilayer-based perpendicular media is subject to a problem associated with conventional magnetic recording media. The magnetic grains must be exchange decoupled in order to improve signal-to-noise ratio (SNR). A typical multilayer recording structure comprises multiple repetitions of Co/Pt or Co/Pd bi-layers which develop strong perpendicular anisotropy. The magnetic layers of the deposited films are granular, with each magnetic grain having a differing composition through its cross section. For these magnetic grains to be able to switch magnetization direction independently of each other (thus increasing SNR), they have to be exchange decoupled.
A solution to this problem has been suggested recently by adding elements such as chromium to a magnetic layer such as Co in the bi-layer structure. Although this approach may help to exchange decouple the magnetic Co grains to some extent, since the non-magnetic Pt and Pd used in perpendicular anisotropy multilayer are highly polarizable elements, the exchange coupling will persist through the Pd or Pd spacer layers.
The present invention has been developed in view of the foregoing, and to address other deficiencies of the prior art.
The present invention effectively exchange decouples grains throughout a multilayer perpendicular magnetic recording structure and also controls the grain size throughout the multilayer structure. In accordance with the present invention, additives such as B, Cr, SiO2, etc. are added to the non-magnetic spacer layers of a multilayer recording structure, as well as to the magnetic layers, in order to decouple grains throughout the entire multilayer structure. Such decoupling in both the non-magnetic spacer layers as well as the magnetic layers not only controls exchange coupling between the grains, but also provides a mechanism to control the grain size.
An aspect of the present invention is to provide a magnetic recording media comprising a substrate and a hard magnetic recording layer on the substrate comprising alternating layers of magnetic material and spacer material, wherein the spacer material is exchange decoupled.
Another aspect of the present invention is to provide a magnetic recording material comprising alternating layers of magnetic material and spacer material, wherein the spacer material is exchange decoupled.
A further aspect of the present invention is to provide a method of making a magnetic recording material. The method comprises depositing alternating layers of exchange decoupled magnetic material and exchange decoupled spacer material.
These and other aspects of the present invention will be more apparent from the following description.